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Which distribution system is more economical in multi-storied buildings?
Phase 4 wire
Phase 2 wire
Phase 3 wire
Phase 5 wire
Phase 4 wire
In multi-storied buildings, the 3-phase 4-wire system is the most economical distribution method because it allows for both 3-phase power (for lifts, pumps) and single-phase power (for lighting, appliances) from the same network. This system utilizes a neutral conductor, enabling the distribution of single-phase loads at phase-to-neutral voltage (VphтАЛ=3тАЛVLтАЛтАЛ) while maintaining 3-phase availability.
In multi-storied buildings, the 3-phase 4-wire system is the most economical distribution method because it allows for both 3-phase power (for lifts, pumps) and single-phase power (for lighting, appliances) from the same network. This system utilizes a neutral conductor, enabling the distribution of single-phase loads at phase-to-neutral voltage (VphтАЛ=3тАЛVLтАЛтАЛ) while maintaining 3-phase availability.
VLтАЛ=3тАЛVphтАЛ тАФ Relationship between Line voltage and Phase voltage in star connection
INтАЛ=IRтАЛ+IYтАЛ+IBтАЛ тАФ Neutral current as the vector sum of phase currents
The 3-phase 4-wire system employs three phase conductors and one neutral conductor connected in a star (Y) configuration. This configuration allows the neutral wire to carry the unbalanced current, providing a stable potential for single-phase loads and eliminating the need for separate transformers for different voltage levels, thus significantly reducing cabling and installation costs in vertical structures.
The 3-phase 4-wire system is the standard for commercial and residential multi-storied buildings.
It supports balanced 3-phase industrial loads and unbalanced single-phase domestic loads simultaneously.
Using a neutral wire prevents floating neutral issues in an unbalanced 3-phase system.
It leads to copper savings in conductors compared to separate single-phase circuits.
Supports both 3-phase and single-phase loads
Balanced voltage supply for lighting loads
Reduced conductor material requirements
Flexibility in load management
Requires careful load balancing between phases to minimize neutral current
Neutral wire must be rated for potential unbalance currents
Residential multi-storied apartments
Commercial office complexes
Industrial floor distribution
According to IS codes, 415V, 50Hz, 3-phase 4-wire supply is standard for building electrification in India.
Option B (2-wire) is typically used for small domestic single-phase supply only, not for multi-storied buildings requiring 3-phase power.
A is correct тАФ The 3-phase 4-wire system provides the most efficient balance of cost and utility for the diverse load requirements of multi-storied buildings.
Always remember that in a Star-connected system, the neutral wire is essential for single-phase loads, which constitutes the majority of power consumption in building electrification.